Pasta Night Particles: Boiling Water and Iced Tea

A Kitchen Lab on Pasta Night

1Friday is pasta night at the Haidari home, which is in a town near sea level. This week, seventh grader Soraya Haidari turned the kitchen into a lab. Her brother Navid, who is 19, handled everything on the stove and everything hot, while Soraya read a digital kitchen thermometer and took notes. In science class, she had learned that all matter is made of tiny particles that are always moving, and that a thermometer measures how fast, on average, those particles move. She wanted to see what happens to water's particles when a kitchen adds thermal energy to them or takes it away.

2Navid filled a pot with 2,000 g of tap water at 20 °C, set it on a burner turned to high and left the lid off. Navid kept the burner on the same setting the whole time, and Soraya held the thermometer's tip in the middle of the water, away from the hot bottom of the pot. Soraya read the water's temperature every 2 minutes (Table 1). At minute 12, Navid turned off the burner and set the pot aside to cool. When the water had cooled, Soraya weighed it again: there were 1,810 g left.

3While the water boiled, Soraya noticed something above the pot. Just above the surface of the water there was a clear gap, as if nothing were there. A few centimeters higher, a white cloud swirled up and then faded into the kitchen air.

4After dinner, Navid made a pot of tea and poured 200 g of hot tea at 80 °C into each of two foam cups. Soraya had left a bowl of ice cubes on the counter until they were at 0 °C and starting to drip. She added 150 g of these ice cubes to Cup A and 250 g to Cup B. She stirred both cups, read the temperature after 10 minutes and then lifted out any ice that was left and weighed it (Table 2).